This invention relates in general to an arrangement for connecting fiber optic cable and more particularly to an improved arrangement for connecting the ends of two single mode fiber optic cables in order to provide for a low loss connection.
When the ends of two optical fibers are to be spliced, the first consideration is to make the connection in such a manner that excessive losses of the light energy will not take place at the splice.
One method presently known for making such a splice is the use of a special machine which prepares the ends of the fibers and also supplies an arc which heats the prepared ends. The fiber ends are then butted together under pressure, bonding the ends together molecularly. A strengthening sleeve is then applied to cover the splice. This method finds disadvantage in that the fiber ends must be perfectly flat and parallel and both fibers must be composed of the same type of fiber.
Another method for effecting a splice of two optical fibers is pressure bonding. This method requires the careful cleaving of each fiber so as to produce ends which are perfectly flat and parallel. The ends are then butted together and a metal jacket applied over each fiber end. This method finds disadvantage in that the preparation of the fiber ends must match exactly or excessive losses will occur. Further, any strain applied to the splice may separate the fibers causing a failure of the splice.
Still another method of splicing optical fibers uses an "optical adhesive" to bond the ends of the fibers after they have been prepared to present flat and parallel end surfaces to one another. A metal jacket is then used to cover the splice in order to give strength to the joint.
In all the above referenced techniques each end of the connecting fibers must be formed perfectly flat and parallel to the other in order to efficiently transmit all the light energy with a minimum signal loss. Additionally, the two fiber optic ends must be positioned precisely along the horizontal axis or coupling losses will result. Given the fact that the core of a fiber optic cable may measure 10 micrometers or less the job of cleaving and grinding the ends to form the proper surfaces for splicing and subsequently aligning the two ends is therefor a very exacting and labor intensive task.
One method presently known for splicing optical fiber cable circumventing the disadvantages discussed above is the use of optical fiber connector units. These high precision components are comprised of a plug ferrule, receptacles and a plug polisher. The connector units resemble those used for coaxial cable and provide connection losses of only 0.5 dB.
The disadvantage with this type of connection is the high per unit cost for these devices. For example, single mode optical fiber connectors manufactured by Seico Instruments cost upward of $400.00 per connector.
Still another disadvantage to optical connectors is that they must be assembled using epoxy adhesives to hold the optical fiber in alignment; the epoxies often require exposure to an ultraviolet curing light or high temperatures. Furthermore if, once the epoxy has cured, the fiber alignment is unsatisfactory, the connector has to be cut off and discarded.
Accordingly, it is the object of the present invention to provide an improved, efficient and cost effective means for connecting or splicing single mode fiber optic cable.